Proton-conductive membranes and layers and methods for their production

ABSTRACT

This invention relates to a silane-resin composition that can be obtained by at least partial hydrolytic condensation of at least the following components: (1) one or more sulfonic acid group-containing silane(s) with at least one group that can be cleaved under hydrolytic conditions, (2) one or more styryl-functionalized silane(s) and (3) one or more silane(s) that carry a nitrogen-containing heterocyclic compound, an amine group or a sulfonamide group with at least one group that can be cleaved under hydrolytic conditions, and mixing of the components before, during or after the hydrolytic condensation, as well as a process for the production of this composition. With the silane resin that is obtained, proton-conductive, organically cross-linked heteropolysiloxanes can be produced that are suitable for PEMFC in a layer or membrane form as proton-conductive systems. Their proton conductivity can be further increased by the addition of suitable liquids.

CROSS-REFERENCED RELATED APPLICATIONS

This application claims priority to German Application Number 101 63518.4, filed Dec. 21, 2001, which is hereby incorporated by reference inits entirety.

This invention relates to proton-conductive layers, especiallymembranes, that are based on co-condensed styryl- andsulfonyl-functionalized alkoxysilanes as well as a process for theproduction of such layers/membranes.

Interest in polymer electrolyte-membrane-fuel cells (PEMFC) for mobileapplications has greatly increased in recent years. Most PEM-fuel cellsystems still use polymer electrolytes that are part of the Nafion®family of perfluorinated, sulfonated ionomers produced by Du Pont ofNemours. The class of perfluorinated, sulfonated materials also includesFlemionTM of Asahi Glass and AciplexTM of Asahi Chemical. In 1987, afuel cell with improved PEMFC output was developed by Ballard AdvancedMaterials Corp. using a membrane made by the Dow Chemical Company. Itwas similar to the Nafion® membrane but had a shorter side chain, inwhich the SO₃H portion and thus the conductivity of the polymer wereincreased. At the same time, Du Pont attempted to increase the value ofits membrane by reduction of the membrane thickness and an increase ofthe SO₃H portion. These polymers, however, are still expensive toproduce which prevents mass production.

The literature discusses several different polymer developments whichattempted to eliminate the high cost of production and allow for massproduction. A possibility of reducing cost is the production of apartially fluorinated polymer. Thus, at the end of the 1980's, e.g.,Ballard started a program for developing economical polymer electrolytesfor fuel cell applications. This resulted in a polymer composite, basedon sulfonated α,β,β-trifluorostyrene and polytetrafluoroethylene (see,e.g., U.S. Pat. No. 5,985,942 and others). During the 1990's, Hoechst AGdeveloped sulfonated poly(aryl ether ketones) (EP 574791 A1); but theoutput of the fuel cells with such membranes was still too low. Anothertechnique to develop proton-exchanger membranes is based on the couplingof styrene (U.S. Pat. Nos. 5,994,426 and 5,656,386, F. N. Büchi et al.,J. Electrochem. Soc. 142, (1995) 3044) or α,β,β-trifluorostyrene (WO99/24497) with a fluorinated polymer, such as polytetrafluoroethylene,and the subsequent sulfonation of the polymer. The electrochemical andmechanical properties of these membranes are inadequate, however, andmust still be improved for use in fuel cells.

In the case of direct-methanol-fuel cells (DMFC) with Nafion membranes,in addition to the cost problems, there is the problem that Nafion onlyallows an operating temperature of at most 90° C. At highertemperatures, the membranes lose the water that is complexed in the—SO₃H groups, which results in a reduction of proton conductivity. Inaddition, these membranes have a high methanol crossover (i.e., methanolpermeability). Therefore, they are not well suited for DMFCapplications.

To reduce this problem, a whole series of anhydrous polymer-protonconductors was developed in recent years, the conductors are produced bycomplexing different polymers with strong acids, such as sulfuric acidor phosphoric acid. This category includes polymers, e.g.,poly(ethylenimines), see, D. Schoolmann et al., Electrochim. Acta 37(1992), 1619, and poly(benzimidazoles), see, U.S. Pat. Nos. 5,716,727,and 5,525,436, J. S. Wainright et al. in “New Materials for Fuel CellSystems II, O. Savadogo and P. R. Roberge Eds., 1997, 808, and J. S.Wainright et al., J. Electrochim. Soc. 142 (1995), L121. The thermalstability and the redox stability, however, are often limited because ofthe high acid concentration and the oxidation potential of the acids.Also, it was attempted, i.a., to improve the Nafion membrane by the useof a three-layer membrane (U.S. Pat. No. 5,981,097) or by an optimizedcatalyst layer (X. Ren et al., Polym. Mater. Sci. Eng. 80 (1999), 601,X. Ren et al., J. Electrochem. Soc. 143 (1996), L12) for the methanoloxidation.

At the end of the 1990's, new systems were studied in which the strongacids were replaced by, e.g., sulfonated poly(aryl ether ketones) andheterocyclic compounds, such as imidazoles or pyrazoles (K.-D. Kreuer etal., Electrochim. Acta 43, 1281 (1998). The latter molecules play therole of a solvent for the acidic protons of the polymers. Good protonconductivity can therefore be achieved with systems that consist of suchheterocyclic compounds and proton-conducting polymers.

In addition, proton-conducting, inorganic-organic polymers have beenproduced based on silanes (ORMOCER®e) that are hydrolytically condensedand polymerized via organic groups, in which sulfonated andsulfonamide-containing groups are bonded into the inorganic network (seeL. Depre, et al., Mat. Res. Soc. Symp. Proc. 575 (2000) 253 and L. Depreet al., Electrochim. Acta 45 (2000), 137). This was achieved using amixture of functionalized alkoxysilanes with sulfonated groups, e.g.,(3-sulfonyl)-1-propenyltrimethoxysilane, alkoxysilanes with sulfonamidegroups, e.g., (2-(4-sulfamoylphenyl)-ethyltrimethoxysilane andalkoxysilanes with polymerizable organic groups such as the epoxy groupin 3-(glycidoxypropyl)methyldimethoxysilane (GLYMO). A hydrolyticcondensation, followed by an organic polymerization, resulted in theproton-conducting membrane. This produced a membrane with a conductivityof 1.4·10⁻² S/cm (12% water, room temperature). These membranes,however, lose their conductivity above 90° C. and show little redoxstability, a basic requirement for fuel cell membranes.

SUMMARY OF THE INVENTION

The invention provides a proton-conducting layer/membrane with excellentconduction properties. The layer/membrane is capable of operating attemperatures above 90° C., and has improved redox stability. In apreferred embodiment, the invention provides membranes that show goodconductivity properties at temperatures in the range of about 140° C.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a Nyquist diagram for a proton-conductive membrane made inExample 3 at room temperature;

FIG. 2 show a Nyquist diagram for the same proton-conductive membrane ofFIG. 1 at a temperature of 120° C.;

FIG. 3 shows a Nyquist diagram for a proton-conductive membrane made inExample 4 at room temperature;

FIG. 4 depicts a synthesis scheme for proton conductinginorganic-organic membranes;

FIG. 5 shows a Nyquist diagram for a proton-conductive membrane made inExample 5 at room temperature.

DETAILED DESCRIPTION

It has been shown according to the invention that layers or membranesbased on hydrolytically condensed silanes can have good conductivityproperties at temperatures that are clearly above 90° C. if they containstyryl-functionalized silanes as network formers. The latter have provento be both more temperature-stable and more redox-stable than previousnetwork formers.

Styryl silanes are known from their use in color particles,oxygen-permeable membranes or electrophotographic materials. In apreferred embodiment, the syrryl silane used is a styrylalkoxysilane.However, the synthesis of these compounds was previously below a yieldof 40%, since the vinyl group during synthesis tends towardpolymerization reactions, and by-products are formed. It has beenpossible for the inventors, however, to improve the exploitation of thisprocess considerably. In this case, styryl-functionalized silanes aresynthesized via a Grignard reagent, whereby the process proceeds in twoseparate steps with use of chlorine-free alkoxysilanes as silanestarting components. It is essential in this case that the production ofthe Grignard compound be carried out in the absence of silane,specifically for suppressing the vinyl group polymerization attemperatures of between about 40-55° C. The solvent that is usedcomprises ether with tetrahydrofuran in the mixing ratio of 30:70 to70:30 (v:v), preferably 50:50 to 60:40. In a preferred embodiment thesolvent consists of essentially ether with tetrahydrofuran in the abovestated ratios. The subsequent reaction of the Grignard compound with thesilane that is selected as an educt should be carried out attemperatures that are not above 20° C., preferably not above 15° C.,whereby the same or a similar solvent can be used, and the temperaturecan be increased to about 40° C. only after the majority of the reactionbatch has been reacted to complete the reaction.

The layers/membranes according to the invention are formed from at leastthree components, namely from (1) sulfonic acid group-containingsilanes, (2) styryl-functionalized silanes, and (3) at least onenitrogen-containing heterocyclic compound, an amine group or silanesthat carry a sulfonamide group. All three components can consist of oneor more silanes of the above-mentioned type. In addition, othercomponents can be present.

At least the silanes that are mentioned above under (1) and (3) have atleast one group that can be cleaved under hydrolytic conditions, so thatthe compounds are accessible to a hydrolytic condensation.

The sulfonic acid group-containing silanes that can be used for theinvention are preferably selected from the silanes of formula (I):P_(a)R¹ _(b)SiX_(4-a-b)  (I)in which P has the meaning of HOSO₂—R—, in which R is or comprises analiphatic or aromatic organic radical, preferably an optionallysubstituted alkylene, alkenylene or phenylene group; R¹ represents agroup that is bonded via carbon to silicon, e.g., optionally substitutedalkyl, alkenyl, alkinyl, aryl, alkylaryl or arylalkyl; X is a group thatdissociates off under hydrolytic conditions; a is 1 or 2; b is 0, 1 or2; and a+b together are 1, 2 or 3. P is bonded via radical R, preferablyvia an existing alkylene, alkenylene or phenylene group, to silicon; ifR is an aliphatic group, the latter preferably has 1-6 carbon atoms,more preferably 2-4 carbon atoms. In a preferred embodiment R ispropylene or propenylene. R¹ can be, e.g., methyl, ethyl, a propylradical (n- or iso-) or a butyl radical (n-, iso- or t-). Thehydrolysis-sensitive radical X can be hydrogen, halogen, alkoxy, aryloxyor NR² ₂ with R² equal to hydrogen or lower alkyl and is preferablyC₁-C₁₂-alkoxy, quite especially preferably C₁-C₄-alkoxy. In a preferredembodiment, a is 1, and b is 0.

The styryl group-containing silanes of this invention are preferablyselected from those of general formula (II)(St)_(a)R¹ _(b)SiX_(4-a-b)  (II)in which (St) is a facultatively substituted styryl radical; R¹ is agroup that is bonded via a carbon atom to silicon, for exampleoptionally substituted alkyl, alkenyl, alkinyl, aryl, alkylaryl orarylalkyl; X is a hydrolysis-sensitive radical; a means 1, 2 or 3; bmeans 0, 1, 2 or 3; and a+b together are 1, 2, 3 or 4. (St) canoptionally be substituted with a group that is bonded via carbon, forexample, alkyl, aryl, alkylaryl or arylalkyl. In preferred embodiments,a+b is not more than 3, i.e., the silane of formula (II) contains one(or else more) hydrolyzable group X. In these cases, the styrylgroup-containing silane can be co-condensed with one silane(s) oranother. In addition, (St)p-vinylphenyl is preferred. R¹ can be, e.g.,methyl, ethyl, a propyl radical (n- or iso-) or a butyl radical (n-,iso- or t-) and is preferably methyl or ethyl. Radical X that can behydrolyzed off can be hydrogen, halogen, alkoxy, aryloxy or NR² ₂ withR² equal to hydrogen or lower alkyl and is preferably C₁-C₆-alkoxy,quite especially preferably C₁-C₄-alkoxy. In a preferred embodiment, ais 1 or 2, and b is 0 or 1.

The silanes that carry at least one nitrogen-containing heterocycliccompound, an amine group or a sulfonamide group are preferably selectedfrom those of general formula (III)(Q)_(a)R¹ _(b)SiX_(4-a-b)  (III)in which radicals R¹ and X and indices a and b are defined as forformula (I); (Q) can be Het—R— or NH₂SO₂—R— or NHR²—R—, whereby R and R²are defined above as for formula (I), and Het is a nitrogen-containingheterocyclic compound in the ring. Radical R of group Q is preferablybonded via an existing alkylene, alkenylene or phenylene group tosilicon; if R is an aliphatic group, the latter preferably has 1-6carbon atoms, more preferably 2-4 carbon atoms. In a preferredembodiment R is propylene or propenylene. R¹ can be, e.g., methyl,ethyl, a propyl radical (n- or iso-) or a butyl radical (n-, iso- ort-). (Het) can be, for example, a five- or six-membered ring, whichcontains one or two nitrogen atoms or a nitrogen atom and an oxygen atomor a sulfur atom. Condensed ring systems are also possible. The nitrogenatoms can be present as —N═ groups or as —NR³ groups with R³ preferablyequal to hydrogen. Examples of suitable heterocyclic compounds arepyrrole or imidazole. The hydrolysis-sensitive radical X can behydrogen, halogen, alkoxy, aryloxy or NR² ₂ with R² equal to hydrogen orlower alkyl and is preferably C₁-C₁₂-alkoxy, and more preferablyC₁-C₄-alkoxy. In a preferred embodiment, a is 1 and b is 0.

The silanes that are described above may be combined in any sequence andoptionally can be hydrolyzed and condensed in the presence of othercomponents such as, e.g., silanes of formula (IV)R⁴ _(a)SiX₄₋₁  (IV)in which X has the meaning that is indicated for formula (I) above, R⁴is optionally substituted alkyl, alkenyl, alkinyl, aryl, alkylaryl orarylalkyl and a is 0 to 4, and/or compounds of formula (V)M(OR⁵)_(c)  (V)in which M is a metal that can form alkoxy groups in aqueous systems,especially Ge, Sn, Pb, Ti or Zr, whereby c is 4, or B or Al, whereby cmeans 3, and R⁵ represents an alkyl or alkenyl, preferably a C₁-C₄alkyl, whereby usually a catalyst is added. In addition, other additivessuch as fillers, pigments, polymerization initiators (e.g., for a UV- ora thermally-initiated polymerization), etc. can be added as needed.

In one embodiment, it is preferred that silanes (1) and (3) first are atleast partially hydrolyzed separately and then are mixed with oneanother once thoroughly condensed. Component (2), i.e., thestyryl-functionalized silane(s), can either also optionally beseparately hydrolyzed/condensed and then mixed only with the condensatesof (1) and (3); but it is preferred that this component be added eitherto one or, more preferably, both of components (1) and (3) in portionsand optionally co-hydrolyzed and co-condensed with the latter.

Consequently, preferably a first solution (A) is produced by ahydrolytic condensation that preferably occurs in the acid range(sol-gel process) with use of at least one sulfonic acidgroup-containing silane and at least one styryl group-containing silane,which preferably has at least one hydrolyzable group. Also, a secondsolution (B) is obtained by hydrolytic condensation (sol-gel process),specifically with use of at least one silane that carries anitrogen-containing heterocyclic compound, an amine group or asulfonamide group as well as a silane that has the same or a differentstyryl group and that also preferably contains at least one hydrolyzablegroup X as mentioned for (A), optionally in the presence of othercomponents. The hydrolysis/condensation of this component (B) ispreferably catalyzed in a basic manner. The hydrolytic condensation ofboth systems is generally carried out in a suitable solvent, e.g., analcohol such as methanol, in which water can be admixed. The twohydrolytically condensed components are mixed, and the resultingsolution is preferably stirred for a while longer.

In an alternative, also preferred embodiment of the invention, thesilane comprising one or more sulfonic acid groups first is at leastpartly hydrolyzed and condensed. Next, the styryl-functionalized silaneand the silane comprising a nitrogen containing heterocycle, an aminefunction or a sulfonamide function are added, together with the amountof water as required for partly or, more preferred, full hydrolysis andco-condensation.

The hydrolytic condensation preferably conducted for a range of severalhours to one or more days.

In many cases, it is especially advantageous if the number of sulfonicacid groups and that of the sulfonamide, amine or heterocycliccompound-nitrogen groups (the latter, if they are basic) in the mixtureto be approximately equal, or else the number of sulfonic acid groupspredominates, since the sulfonic acid groups act as proton donors, andthe sulfonamide, amine and the basic heterocyclic compound-nitrogengroups act as proton acceptors. The layer that is produced from thesecomponents thus acts in a proton-conducting manner. The amount of styrylgroups is selected based on the desired mechanical properties of themembrane that is to be produced. For example, an amount of 20-60 mol %,relative to the amount of silicon atoms, is suitable. A preferred amountof styryl groups is 30-50 mol %, with about 40 mol %, being mostpreferred.

After the condensation has been completed, existing solvent isoptionally removed, e.g., distilled off. If it is necessary, solvent canalso be added, or a solvent exchange can take place. In a suitable way,the resulting resin has a viscosity that allows it to be poured intomolds or forms, e.g., Teflon or aluminum molds, or spread out/stretchedon substrates. In such a form, it can advantageously be hardened bythermal or UV-polymerization of the styryl groups. Polymerization may beaccomplished through UV, thermal, combinations thereof or otherprocedures known in the art. For UV polymerization, photo-initiatorssuch as Irgacure 369 can be used, and for thermal polymerization,thermal initiators such as dibenzoyl peroxide can be used. In the caseof thermal polymerization, starting from about 70° C., an initiator canalso be eliminated, since starting from about 50° C., reactive radicalsof the styryl groups begin to form. Thermal curing not only begins thepolymerization, but also is useful in evaporating the solvent residueswhich may still be present. Thus, thermal curing, alone or incombination with UV polymerization, may be especially well suited forcertain embodiments. The resulting resin may be stored until requiredunder suitable conditions, for instance −20° C.

The conductivity of the layers or membranes produced may also haveimproved conductivity-increasing substances, which can be used asvehicles for the proton transport on or through the layer or membrane,are added to them before or after the cross-linking. Examples of thisare substances such as water or imidazole that can play the role of asolvent for acid protons. Other examples can be found, for example K. D.Kreuer et al., Electrochimica Acta 43, 1281 (1998). Many of theseliquids, e.g., water, can be adsorbed from the layer or film that hasalready been thoroughly organically polymerized. It can therefore beadded, as desired, before or after the organic polymerization. Othersubstances, e.g., imidazole, are taken up or stored from the finishedlayer or membrane only gradually or not at all, herefore it isrecommended addition to the silane-resin composition occur before theorganic polymerization. In preferred embodiments of the invention, thelayer or membrane therefore provides the opportunity to adsorb water,e.g., in the form of atmospheric moisture, or imidazole which is addedbefore, during or after the solvent that is used for thehydrolysis/condensation is removed and before an organic cross-linkingtakes place.

The below examples are meant to further illustrate the invention andshould not be viewed as limiting the scope or spirit of the invention.

EXAMPLES Example 1 Synthesis of p-Vinylphenylmethyldiethoxysilane

In a three-neck flask under argon and while being stirred mechanically,11.7 g (480 mmol) of magnesium chips and some iodine crystals in 40 mlof a solution A (55% diethyl ether, 45% tetrahydrofuran) are mixedtogether. Then, a solution of 80.0 g (436 mmol) of bromostyrene,dissolved in 210 ml of solvent mixture A, is slowly added in drops, andthus a continuous exothermic reaction is achieved. The solution isstirred under reflux. After the end of the exothermic reaction, thereaction mixture is cooled to 2° C., and then 155.5 g (872 mmol) ofmethyltriethoxysilane in 160 ml of dry diethyl ether is added; thetemperature must not exceed 15° C. After the end of the substitutionreaction, stirring is continued at room temperature overnight.Approximately 200 ml of n-heptane is then added, thus the magnesiumsalts precipitate. The latter are filtered off, 9.7·10⁻² g (0.44 mmol)of 2,5-di-tert-butylhydroquinone is added to the filtrate, the solventis drawn off in a rotary evaporator, and the residue is distilled infractionated form under vacuum. 72.5 g (307 mmol) of the product wasobtained with a yield: 70.3%, and a boiling point of 65-66° C. (0.05mbar)

Example 2 Synthesis of p-Vinylphenyltrimethoxysilane,Bis-(p-vinylphenyl)-dimethoxysilane andTris-(p-vinylphenyl)-methoxysilane

Styryl magnesium bromide is produced as in Example 1. Then, 39.9 g (262mmol) of tetramethoxysilane in 80 ml of dry diethyl ether is added tothe cold solution (2° C.) of the Grignard reagent. After the addition,the batch is heated for one and one-half hours to 45° C., thus thesubstitution proceeds fully, and then it is stirred overnight at roomtemperature. The batch is worked up as in Example 1. After the solventis removed, 105.3 g of a light yellow mixture is obtained.²⁹Si-NMR-spectroscopy shows that the crude product containsp-vinylphenyltrimethoxysilane, bis-(p-vinylphenyl)-dimethoxysilane andtris-(p-vinylphenyl)-methoxysilane.

The mono- and di-substituted alkoxysilanes are separated by distillationfrom the crude product and purified:

-   -   15.8 g (70.5 mmol) of vinylphenyltrimethoxysilane        (mono-substituted alkoxysilane), yield 34.9%, boiling point:        59-60° C. (0.03 mbar)    -   24.5 g (82.8 mmol) of bis-(p-vinylphenyl)-dimethoxysilane        (disubstituted alkoxysilane), yield: 41.0%    -   Total yield: 75.9%

In addition, tris-(p-vinyl-phenyl)-methoxysilane could be detected byspectroscopy in the residue.

Example 3 Synthesis of a Proton-conductive Membrane

A (3-Sulfonyl)-1-propenyltrimethoxysilane  1.1 g (4.5 · 10⁻³ mol) Bp-Vinylphenylmethyldiethoxysilane 0.71 g (3.0 · 10⁻³ mol) Cp-Vinylphenylmethyldiethoxysilane 0.71 g (3.0 · 10⁻³ mol) DN-(3-Triethoxysilylpropyl)-4,5-  1.2 g (4.5 · 10⁻³ mol) dihydroimidazole

In a first flask, components C, D and 2.4 g (7.5·10⁻² mol) of methanolare mixed together at room temperature. Next, 0.17 g (9.7·10⁻³ mol) ofwater is added to this. After 24 hours, components A, B and 1.6 g(5.0·10⁻² mol) of methanol are mixed together at room temperature andthen 0.17 g (9.7·10⁻³ mol) of water is added. After another 24 hours,the two systems are mixed together. The batch is stirred for another 24hours. Then 1.2 g (1.8·10⁻² mol) of imidazole is added, and the solventis removed (in a rotary evaporator). After being spun off, a moderatelyviscous resin is obtained that is hardened after application as a layer,e.g., on a Nafion film or as a membrane by introduction in a Teflon forminto the furnace at 65° C. The conductivity is measured on a membranetablet with a “Schlumberger frequency response analyzer 1260.” TheNyquist diagram indicates the resistance of the sample. (FIG. 1) FIG. 1shows a selected sample with a diameter of 1.15 cm and a thickness of1.5 mm at room temperature. The resistance is 922 Ω, with a conductivityof 1.6·10⁻⁴ S/cm. The resistance at 120° C. is 23.5 Ω, with anunexpectedly high conductivity of 6·10⁻³ S/cm. This can be seen in thecorresponding diagram, FIG. 2. The same composition, but without theaddition of imidazole, results in a conductivity of 7.6·10⁻⁷ S/cm atroom temperature. If the sample is added to water instead of imidazole(absorption of 20%), then a conductivity of 2.2·10⁻⁴ S/cm is achieved atroom temperature.

Example 4 Production of a Proton-conductive Membrane with a DifferentComposition

A (3-Sulfonyl)-1-propenyltrimethoxysilane  1.2 g (5.0 · 10⁻³ mol) Bp-Vinylphenylmethyldiethoxysilane 0.39 g (1.7 · 10⁻³ mol) Cp-Vinylphenylmethyldiethoxysilane 0.66 g (2.8 · 10⁻³ mol) DN-(3-Triethoxysilylpropyl)-4,5- 0.46 g (1.7 · 10⁻³ mol) dihydroimidazole

This membrane was produced as in Example 3. The resistance of a selectedsample (diameter: 1.15 cm, thickness: 0.12 cm) with a content of 1.02 g(1.5·10⁻² mol) of imidazole is 113 Ω, which results an unexpectedly highconductivity of 1.0·10⁻³ S/cm at room temperature. The Nyquist diagramof this sample is shown in FIG. 3.

Example 5 Synthesis Route of Proton Conducting Inorganic-OrganicMembranes

In the synthesis route of the scheme in FIG. 4, the sulfonated silane isfirst hydrolyzed and condensed. One day later, the styryl-functionalizedalkoxysilane and the alkoxysilane containing at least a nitrogenheterocycle, an amino function or a sulfonamide function are added withthe necessary amount of water for their hydrolysis and co-condensation.Following additional stirring (several days), the solvent is evaporatedat 35° C. under vacuum and the resulting resin can be stored at −20° C.

The resin is cast in aluminum moulds or applied on a substrate as a filmand both thermally and UV-cured. The thermally curing will allow notonly to start the organic polymerization, but also to evaporate theresidues of solvent. The conductivity of the sample can here also beenhanced either by water uptake or by adding imidazole to the sol beforesolvent evaporation. The synthesis route is further depicted in FIG. 4.

For example, the synthesis of a proton conducting membrane following thesynthesis route of FIG. 4 comprises the following:

Trimethoxysilylpropylsulfonic acid  1.1 g (4.5 · 10⁻³ mole)p-Vinylphenylmethyldiethoxysilane 0.44 g (1.9 · 10⁻³ mole)N-(3-triethoxysilylpropyl)-4,5- 0.31 g (1.1 · 10⁻³ mole)dihydroimidazole

In a first step trimethoxysilylpropylsulfonic acid and 1.4 g (4.5·10⁻²mole) methanol were stirred at room temperature. Then 0.12 g (6.7·10⁻³mole) of water was added. After 24 hoursp-vinylphenylmethyldiethoxysilane,N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole, 0.96 g (3.0·10⁻² mole)methanol and 7.1·10⁻² g (3.9·10⁻³ mole) water were added. The reactionmixture was stirred for six days. Next, 0.95 g (1.3·10⁻² mole) imidazolewas added and the solvent was evaporated at 35° C. under vacuum. Afterthe evaporation a middle viscous resin was obtained, a starter for thestyrene UV-polymerization was added. The resin was cast in aluminummoulds or coated on a substrate like a Nafion®-foil, pre-baked at 70° C.for two hours and UV-polymerized for two minutes. The FIG. 5 shows theNyquist-diagram at room temperature of a selected sample with a diameterof 1.15 cm and a thickness of 400 μm with a resistance of 145 Ω. Thesample has a conductivity of 2.7·10⁻⁴ S/cm. At 115° C., a resistance of3.9 Ω was measured, and the sample had a conductivity of 1.0·10⁻² S/cm.FIG. 5 provides a Nyquist-diagram of an ORMOCER®/imidazole sample fromthe above synthesis route.

1. Silane-resin composition, obtained by (i) at least partiallyhydrolytic condensation of at least the following components: (1) One ormore sulfonic acid group-containing silane(s) with at least one groupthat can be cleaved under hydrolytic conditions, selected from silanesof formula (I):P_(a)R¹ _(b)SiX_(4-a-b)  (I) in which P has the meaning of HOSO₂—R,whereby R is an aliphatic or aromatic organic radical or contains such aone, and P is bonded via the latter to the silicon atom; R¹ represents agroup that is bonded to the silicon atom via a carbon atom; X is a groupwhich is sensitive to hydrolysis; a is 1 or 2; b is 0, 1 or 2; and a+btogether are 1, 2 or 3, (2) one or more styryl functionalized silane(s),selected from those of general formula (II)(St)_(a)R¹ _(b)SiX_(4-a-b)  (II) in which (St) is an optionallysubstituted styryl radical; radicals R¹ and X are defined as in formula(I); a means 1, 2 or 3; b means 0, 1, 2 or 3; and a+b together are 1, 2,3 or 4, and (3) One or more silane(s) that carry a nitrogen-containingheterocyclic group, an amine group, or a sulfonamide group and havingattached thereto at least one group that can be cleaved under hydrolyticconditions, selected from those of general formula (III)(Q)_(a)R¹ _(b)SiX_(4-a-b)  (III) in which radicals R¹ and X and indicesa and b are defined as in formula (I); (Q) is Het-R— or NH₂SO₂—R— orNHR²—R—, whereby R is defined above as in formula (I), R² meanshydrogen, and Het is a heterocyclic group containing a nitrogen atombound within the ring, (ii) wherein either the components are mixedbefore hydrolytic condensation, or mixing is performed during or afterhydrolytic condensation of the components.
 2. Silane-resin compositionaccording to claim 1, in which at least one of the radicals and indicesbelow in formulas (I), (II) or (III) has the following meaning: (St) isp-vinylphenyl, Het is an optionally substituted pyrrole, imidazole ordihydroimidazole radical, R is an optionally substituted alkylene,alkenylene or phenylene group, R¹ is a substituted alkyl, alkenyl,alkinyl, aryl, alkylaryl or arylalkyl, X is hydrogen, halogen, alkoxy,aryloxy or NR² with the meaning of R² that is indicated for formula(III), for formulae (I) and (III), a is 1, while for formulae (II), a is1 or 2, b is 0 or
 1. 3. Silane-resin composition according to claim 2,wherein R¹ is methyl, ethyl, n- or i-propyl, or n-, i- or t-butyl, and Xis alkoxy.
 4. Silane-resin composition according to claim 3, wherein Xis C₁-C₄-alkoxy.
 5. Silane-resin composition according to claim 2, inwhich (1)The sulfonic acid group-containing silanes of formula (I) areselected from (ω-sulfonyl)-1-alkyl- or -alkenyl-trialkoxysilanes, (2)the styryl group-containing silanes of formula (II) are selected fromp-vinylphenylalkyldialkoxysilanes, and (3) the silanes of formula (III)that carry at least one nitrogen-containing heterocyclic group, an aminegroup or a sulfonamide group are selected from N-(trialkoxysilylalkyl or-alkenyl)-4,5-dihydroimidazoles and 2-(trialkoxysilylalkyl- or-alkenyl)imidazoles.
 6. Silane-resin composition according to claim 1,obtained by the following steps: (a) Hydrolyzation and condensation,carried out at least partially, of a mixture (A) that consists of orthat contains at least one sulfonic acid group-containing silane asdefined in claim 1 and at least one styryl-functionalized silane asdefined in claim 1, (b) Hydrolyzation and condensation, carried out atleast partially, of a mixture (B) that consists of or that contains atleast one silane that carries a nitrogen-containing heterocyclic group,an amine group or a sulfonamide group as defined in claim 1 and at leastone styryl-functionalized silane as defined in claim 1, (c) Combinationof mixtures (A) and (B) and optionally additional hydrolyzation andcondensation of the mixture components, whereby a silane resincomposition is obtained.
 7. Silane-resin composition according to claim6, wherein the hydrolyzation and condensation steps are carried out in asuitable solvent, and after the end of step c), d) the solvent isremoved or at least partially removed and/or is at least partiallyexchanged for a substance that increases the proton conductivity. 8.Silane-resin composition according to claim 7, wherein the substancethat increases the proton conductivity is imidazole.
 9. Silane-resincomposition according to claim 1, obtained by the following steps: (a)Hydrolyzation and condensation, carried out at least partially, of atleast one sulfonic acid group-containing silane as defined in claim 1(b) Addition of at least one styryl-functionalized silane as defined inclaim 1 and of at least one silane that carries a nitrogen-containingheterocyclic group, an amine group or a sulfonamide group as defined inclaim 1 to the (partial) hydrolyzate/(partial) condensate obtained instep (a), and (c) Continuation of hydrolyzation and condensation of thecomponents of the mixture, whereby a silane resin composition isobtained.
 10. Silane-resin composition according to claim 9, wherein thehydrolyzation and condensation steps are carried out in a suitablesolvent, and after the end of step c), d) the solvent is removed or atleast partially removed and/or is at least partially exchanged for asubstance that increases the proton conductivity.
 11. Silane-resincomposition according to claim 10, wherein the substance that increasesthe proton conductivity is imidazole.